Lignin Structure Research Articles

Microstructural optimization of lignin‐based carbon fiber: Effects of purification and high‐temperature heat treatment

AbstractLignin is a renewable biomass polymer with a carbon content of more than 60% and has been extensively studied for making lignin‐based carbon fibers (CFs). However, impurities and high carbohydrate content in lignin materials severely limit their molding in melt spinning, and pre‐oxidation and carbonization processes also affect the subsequent preparation of CFs. This paper presents a detailed study of lignin‐based carbon fiber preparation. Pretreatment increased lignin's decomposition temperature to 302.1°C and enabled melt‐spun fiber preparation. Then, pre‐oxidation and carbonization of lignin fibers were further discussed. The pre‐oxidized fibers prepared at 280°C and 0.4°C min−1 have high thermal stability and excellent carbonization performance. The lignin‐based carbon fibers (LCFs) prepared at 1100°C and 3°C min−1 have the highest degree of graphitization, and the surface is smooth without obvious holes. Under these conditions, LCFs have a graphitization degree of 1.50 and conductivity of 62.50 S cm−1, making them suitable for sensors and capacitors.Highlights Effects of pretreatment on lignin structure and properties have been studied. Effects of pre‐oxidation and carbonization on the lignin fibers were studied. Lignin‐based carbon fibers with high conductivity were obtained.

Modulation of improved lignin structure for conversion of iron oxides on the metal artifact

This research reveals the structural analysis and antioxidant properties of unmodified ethanol organosolv lignin (AH EOL) and modified ethanol organosolv lignin (AHD EOL and AHPB EOL) upon incorporation with 1,5-dihydroxy naphthalene and p-benzoquinone, respectively. The extracted lignin derived from OPF was then evaluated with FTIR NMR, GPC, thermal analyses (TGA and DSC), solubility test, and antioxidant activity. Modified ethanol organosolv lignin incorporated with p-benzoquinone (AHPB EOL) exhibited the smallest lignin matrix, which leads to the highest water solubility and antioxidant activity compared to other ethanol organosolv lignin (EOL) samples (D% AHPB EOL: 24.25 ± 0.13 % > D% AHD EOL: 22.50 ± 0.16 % > D% AH EOL: 20.50 ± 0.22 %). The extracted EOL samples derived from OPF were then utilized in a preliminary rust conversion study of a metal artifact, which indicated that 7 wt% AHPB EOL possessed the highest RT% with 88.81 ± 0.14 %. The XRD and surface analysis of the treated rust also showed that it had transformed the archeological rust into an amorphous phase.

Exploring the Photocatalytic Cleavage Pathway of the β-5 Linkage Lignin Model Compound on Carbon Nitride.

As a globally abundant source of biomass, lignocellulosic biomass has been the centre of attention as a potential resource for green energy generation and value-added chemical production. A key component of lignocellulosic biomass, lignin, which is comprised of aromatic monomers, is a potential feedstock for value added chemical production. The cleavage processes of the linkages between monomers to obtain high value products, however, requires significant investigation as it is a complex, non-facile process. This study focuses on the photocatalytic valorization of a β-5 lignin model compound, a key linkage in the lignin structure. It was found that greater yields of aromatic products were obtained from the photocatalytic conversion of β-5 lignin model compound using carbon nitride (CN) when compared to Evonik P25 titanium dioxide (TiO2). Products of the β-5 model compound photocatalytic conversion were determined and C-C bond cleavage was observed. It was also determined that the solvent participated in the reactions with the introduction of a cyano group to one of the products. Radical quenching experiments revealed that superoxide radicals participated in the CN photocatalytic conversion. These results reveal for the first time the products and possible mechanism of the photocatalytic transformation of β-5 model compounds using CN photocatalysis.

Mild degradation of corncob extract 1 residue in a novel sodium metavanadate and aqueous hydrogen peroxide/acetic anhydride system for monophenolic compounds

An efficient and environmentally benign binary mild oxidative degradation method, consisting of a novel sodium metavanadate and aqueous hydrogen peroxide/acetic anhydride (SM-AHPO/AAH) system, was used to convert corncob extraction residue (CCER) for producing monophenolic compounds (MPCs). The SM-AHPO/AAH system demonstrates excellent performance for producing MPCs in a high yield from CCER and CCER conversion to soluble portion (SP) is ca. 97.7 wt%. According to multiple analyses the SP is rich in aromatics. The SM-AHPO/AAH system is also effective for oxidatively degrading other lignin-rich raw materials to producing aromatics as the main products. In the initial step, H2O2 breaks a >C-O- bond in a peroxy chain of lignin structure to produce phenylpropanoid, followed by H2O2 attacking Cβ and Cα to producing H, G and S-type aromatics.

A new strategy to prepare bio-based polylactic acid modifier for multi-functionality: Dopamine-grafted modified lignin

Currently, to address the performance deficiencies associated with high brittleness, inadequate thermal stability, and susceptibility to hydrolysis in polylactic acid (PLA), it is common practice to incorporate multiple or high proportions of additives. However, this approach raises concerns regarding interface compatibility, energy consumption, and environmental impact. In this context, we introduce an environmentally friendly, bio-based PLA modifier that is facile to prepare and facilitates multi-functional applications at a minimal dosage. The presence of a benzene ring structure in lignin endows the material with ultraviolet (UV) resistance, thermal stability, and hydrophobic characteristics, while the exceptional adhesion properties of polydopamine (PDA) enhance interfacial compatibility. A novel biomass polylactic acid modifier, designated as OL@PDA, has been synthesized by modifying low-molecular-weight lignin (OL) with PDA. Comparative analysis of OL@PDA/PLA composite materials reveals a 14.08 % increase in tensile strength and a 42.00 % enhancement in elongation at break relative to pure PLA. The incorporation of the lignin-derived benzene ring structure effectively transforms PLA from a hydrophilic to a hydrophobic material. Furthermore, the UV transmittance at 400 nm (T400 nm%) is recorded at 65.8 % for pure PLA, which significantly decreases to below 5 % for OL@PDA/PLA composites. The integration of OL@PDA as a modifier in PLA materials yields comprehensively performance enhancements while maintaining a low additive concentration.

Assessing the potential for upscaling the continuous production of lignin oils through reductive catalytic depolymerization

Lignin represents up to one third of lignocellulosic biomass and is a sustainable carbon source available at a sufficient scale to replace an impactful amount of fossil resources when converted into materials and chemicals. The molecular structure of lignin renders it ideal to obtain renewable aromatic building blocks for the polymer industry. Nevertheless, in polymeric form, lignin poses serious challenges for material applications and chemical conversion, namely poor solubility, and low reactivity. This problem can be circumvented by depolymerization of isolated lignins. To meet the demand for renewable aromatic building blocks, it is crucial to utilize technical lignin streams generated on large scale. This will eventually allow the development of continuous, high-throughput processes which are required for viable industrial-scale operations. Our work demonstrates for the first time that “technical grade” hydrolysis lignin from an operating biorefinery can be successfully subjected to continuous reductive catalytic depolymerization (RCD) in a packed bed reactor using a commercially available Pd/Al2O3 catalyst. The impact of catalyst amount, feed concentration (in methanol), and temperature with regards to process stability and product quality was investigated. The product was characterized by NMR, GPC, and GC-FID. Feed concentrations up to 7 wt% could be continuously processed for 77 h at 200 °C whereas at 225 °C, the operation time was restricted to 21 h. In all cases, a stable output was obtained over time in terms of molar mass, OH-group distributions, and monomer content. At 200 °C, carbon yields above 90 % of the soluble lignin fraction were feasible.

Unlocking full potential of bamboo waster: Efficient co-production of xylooligosaccharides, lignin, and glucose through low-dosage mandelic acid hydrolysis with alkaline processing

Mandelic acid (MA), a natural and environmentally friendly organic acid, demonstrates high selectivity and efficiency in hydrolyzing hemicellulose, making it an excellent candidate for xylooligosaccharides (XOS) production at low acid dosages. Despite its potential, the application of MA for XOS production has not been evaluated. The study first investigated the effectiveness of MA in hydrolyzing hemicellulose in bamboo into XOS. Under optimized conditions (50 mM MA, 180 °C, 45 min), a high XOS yield of 65.9 % was achieved, with a total xylobiose and xylotriose yield of 43.5 %. Subsequent alkaline pretreatment enabled 92.1 % lignin removal from MA-pretreated bamboo. The recovered lignin exhibited a high purity of 95.2 % and retained fundamental structure and functional groups of native lignin. The resulting residue displayed enhanced crystallinity and accessibility, with reduced hydrophobicity and surface area lignin compared to untreated bamboo. At high substrate concentration of 20 %, cellulase hydrolysis resulted in a glucose conversion efficiency of 83.9 %. Overall, this integrated strategy offered an efficient approach for the co-production of valuable XOS, lignin, and glucose from bamboo. The efficient energy utilization and economic viability further highlight the potential of this method for large-scale industrial applications, making it an attractive option for biomass valorization.

Enhancement of hydrogen production in dark fermentation of corn stover hydrolysates through composite electric field pretreatment: Improving enzymatic efficiency and regulating microbial metabolic balance

This study investigates the effects of composite electric field pretreatment (CEP) on hydrogen production from corn stover enzymatic hydrolysates in dark fermentation. The findings reveal that under optimal conditions, the CEP group achieved a cumulative hydrogen yield of 77.3 ± 2.6 mL/g TS, marking a 55.3 % increase compared to the control group without the electric field. CEP significantly enhances the fermentation capacity of enzymatic hydrolysates during the acid-stage of dark fermentation by disrupting the lignin structure and optimizing cellulase hydrolysis efficiency. Additionally, pH self-regulation is facilitated through the interaction between volatile fatty acids (VFAs) and ammonia nitrogen. Microbial community analysis revealed that CEP shifts the metabolic balance between Clostridium_sensu_stricto_1 and Lactococcus, leading to increased hydrogen yield and concentration during acid fermentation. Notably, Terrisporobacter exhibited a superior acid-producing capability compared to Bacteroides during the dark fermentation of enzymatic hydrolysates. This study provides a new perspective for the practical application of corn stover.

Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics

Uncovering the structure of lignin from biorefinery has an important effect on lignin catalytic depolymerization and the production of bioenergy. In this study, two biorefinery lignins were isolated from tobacco stalks via alkaline and deep eutectic solvent (DES) catalyzed delignification processes, and the lignin heterogeneity structural characteristics were elucidated by gel permeation chromatography, 2D-HSQC, FT-IR, etc., to understand the relationship between the structure and the thermal characteristics of lignin. It was found that the lignins presented various structural characteristics and components, in which the predominant interunit linkages of black liquor lignin are β-O-4 and β-β linkages, and the β-O-4 linkages disappeared by DES treatment. DES lignins exhibited lower molecular weights and yields than black liquor lignin. Thermogravimetric analysis and fixed-bed pyrolysis were also performed to investigate the lignin thermal behavior. The results show that the DES approach can improve the bio-oil production from lignin and highlight the potential of DES lignin as a promising feedstock in the lignin pyrolysis process. This work provides a valuable example of the conversion of biorefinery lignin into pyrolysis products.

Exploring the relationship between lignin structure and antioxidant property using lignin model compounds

Lignin has a natural polyphenol structure that is expected to replace chemically synthesized antioxidants as a native antioxidant with biodegradable and convenient source characteristics. However, the improvement of the antioxidant property of lignin and its application as an antioxidant are still somewhat limited due to the lack of understanding of the relationship between specific lignin structures and antioxidant property. Therefore, the study of the relationship between lignin structure and antioxidant property is crucial to realize the high-quality application of lignin. In this experiment, the scavenging ability of free 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radicals was determined for different grades of acetylated tannins, typical lignin model compounds and different structural units of milled wood lignin to investigate the relationship between lignin structure and antioxidant property. Based on the experimental results, some structure-activity relationships were proposed and the mechanism of the antioxidant property of lignin was discussed. The number of phenolic hydroxyl groups was linearly and positively correlated with antioxidant property, and the scavenging of DPPH radicals increased significantly with the increase in the number of methoxy groups in the model compounds. Moreover, aldehyde and carboxyl groups had a negative effect on the antioxidant property of lignin, while methoxy, alkyl and alcohol hydroxyl groups played a positive role. The guaiacyl (G) and syringyl (S) units favored the antioxidant property, so the difference in the content of structural units in lignin under certain conditions of phenolic hydroxyl content also affected the antioxidant property. Therefore, the antioxidant property of aspen milled lignin was higher than that of other milled lignin from different wood species. Finally, the mechanism of DPPH free radical scavenging by lignin was revealed to better understand the relationship between lignin structure and antioxidant property.

Conversion of Lignin to Nitrogenous Chemicals and Functional Materials.

Lignin has long been regarded as waste, readily separated and discarded from the pulp and paper industry. However, as the most abundant aromatic renewable biopolymer in nature, lignin can replace petroleum resources to prepare chemicals containing benzene rings. Therefore, the high-value transformation of lignin has attracted the interest of both academia and industry. Nitrogen-containing compounds and functionalized materials are a class of compounds that have wide applications in chemistry, materials science, energy storage, and other fields. Converting lignin into nitrogenous chemicals and materials is a high-value utilization pathway. Currently, there is a large amount of literature exploring the conversion of lignin. However, a comprehensive review of the transformation of lignin to nitrogenous compounds is lacking. The research progress of lignin conversion to nitrogenous chemicals and functional materials is reviewed in this article. This article provides an overview of the chemical structure and types of industrial lignin, methods of lignin modification, as well as nitrogen-containing chemicals and functional materials prepared from various types of lignin, including their applications in wastewater treatment, slow-release fertilizer, adhesive, coating, and biomedical fields. In addition, the challenges and limitations of nitrogenous lignin-based materials encountered during the development of applications are also discussed. It is believed that this review will act as a key reference and inspiration for researchers in the biomass and material field.

Lignin-based monophenolic model compounds in L-tyrosine derivative synthesis via tyrosine phenol lyase

Tyrosine phenol lyase (TPL) synthesises L-tyrosine derivatives from monophenols, pyruvate and ammonia. Production of such high-value aromatic chemicals from biomass-derived raw materials is of great interest. In this study, six monophenols (guaiacol, phenol, o-cresol, m-cresol, catechol and syringol) were chosen based on the structure of lignin and were studied as substrates in the enzymatic reaction. Single monophenol reactions (SMR) and binary monophenol reactions (BMR) with guaiacol were carried out. TPL-M379V was found to be selective towards guaiacol (84.5 % conv.). The highest single activity was measured towards phenol (93.9 % conv.). However, the enzyme preferred guaiacol over phenol in the BMRs. Syringol was found to be inert in the reaction, whereas catechol had an inhibitory effect on the enzymatic reaction, in addition to causing degradation of all the substrates in the medium. Doubling the guaiacol concentration in the SMR did not significantly increase the production of 3-O-methyldopa (conv. 45.9 %). However, in the binary reaction systems the total monophenol conversions were higher with guaiacol and phenol (total 62.4 %) or o-cresol (total 57.1 %). This indicates possible substrate/product specific inhibition. The study provides new data on activity, selectivity and inhibitory effects of monophenols in the synthetic reaction catalysed by TPL-M379V, especially in mixed-substrate reactions.

The Chemical Structure, Extraction Method, and Biological Activity of Lignin–Carbohydrate Complexes

The Chemical Structure, Extraction Method, and Biological Activity of Lignin–Carbohydrate Complexes

A lignin-based controlled/sustained release hydrogel by integrating mechanical strengthening and bioactivities of lignin

The favorable antioxidant and antimicrobial activities of lignin have been shown to promote wound healing. However, the accumulation of lignin in high concentrations in the body brings about varying degrees of biotoxicity. Herein, a controlled/sustained release polyvinyl alcohol/chitosan/sulfonated lignin hydrogel (PVA-CS-L) integrated mechanical strengthening and bioactivities of lignin was developed. The lignin-induced non-covalent bond network (van der Waals force, hydrogen and electrostatic interactions) promoted energy dissipation when the hydrogel was subjected to stretching and compression. This endowed the PVA-CS-L hydrogel with improved tensile (∼36 kPa) and compressive strength (∼900 kPa), as well as compressive toughness (∼9.0 MJ/m3), which were superior to the polyvinyl alcohol/chitosan hydrogel (PVA-CS) (31 kPa, 680 kPa, and 7.5 MJ/m3, respectively). The construction of electrostatic interaction could not only slow down the sudden release of lignin but also make the hydrogel exhibit a good pH-sensitive behavior of controlled-release lignin. Also, the developed hydrogel had good biocompatibility and the released lignin had reactive oxygen species scavenging as well as inhibitory activity against Staphylococcus aureus. Finally, preliminary evaluation of drug delivery reveals that the presence of lignin enabled the hydrogel to exhibit longer-lasting controlled/sustained epigallocatechin gallate release properties. Such lignin-based controlled/sustained release hydrogel that integrates the molecular structure and biological difunctional features of lignin gives new insight into cost-effective, easy-to-operate manufacturing of load-bearing and bioactive materials.

Altered Lignin Accumulation in Sorghum Mutated in Silicon Uptake Transporter SbLsi1.

Sorghum [Sorghum bicolor (L.) Moench] has been receiving attention as a feedstock for lignocellulose biomass energy. During the combustion process, the ash containing silicon (Si) can be produced, which causes problems in furnace maintenance. Hence, lowering Si content in the plants is crucial. Nevertheless, limiting Si supply to crops is difficult in practice because Si is abundant in soil. Previously, a Si uptake transporter (SbLsi1) has been identified, and the Si-depleted mutant has also been generated in the model sorghum variety BTx623. In this study, we aim to investigate the change induced by the mutation of SbLsi1 on the accumulation and the structure of lignin in cell walls. Through chemical and NMR analyses, we demonstrated that the lsi1 mutation resulted in a significant increase in lignin accumulation levels as well as a significant reduction in Si content. At least some of the modification was induced by transcriptional changes, as suggested by the upregulation of phenylpropanoid biosynthesis-related genes in the mutant plants. These findings derived from the model variety would be useful for the future development of practical cultivars with high biomass and less Si content for bioenergy applications.

Computational study on the impact of linkage sequence on the structure and dynamics of lignin.

Lignin, one of the most abundant biopolymers on Earth, is of great research interest due to its industrial applications including biofuel production and materials science. The structural composition of lignin plays an important role in shaping its properties and functionalities. Notably, lignin exhibits substantial compositional diversity, which varies not only between different plant species but even within the same plant. Currently, it is unclear to what extent this compositional diversity plays on the overall structure and dynamics of lignin. To address this question, this paper reports on the development of two models of lignin containing all guaiacyl (G) subunits with varied linkage sequences and makes use of all-atom molecular dynamics simulations to examine the impact of linkage sequence alone on the lignin's structure and dynamics. This work demonstrates that the structure of the lignin polymer depends on its linkage sequence at temperatures above and below the glass transition temperature ( ), but the polymers exhibit similar structural properties as it is approaching the viscous flow state (480 K). At low temperatures, both of lignin models have a local dynamics confined in a cage, but the size of cages varies depending on structural differences. Interestingly, at temperatures higher than , the different linkage sequence leads to the subtle dynamical difference which diminishes at 480 K.

Insights into the Chemical Structure and Antioxidant Activity of Lignin Extracted from Bamboo by Acidic Deep Eutectic Solvents.

Deep eutectic solvents (DESs) composed of choline chloride as hydrogen bond acceptors (HBAs) and six organic acids as hydrogen bond donors (HBDs) were used to extract lignin from bamboo (Phyllostachys edulis (Carrière) J. Houz.). The structures of the DES-extracted lignin samples were analyzed by Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-vis), thermogravimetric analysis (TG), and gel permeation chromatography (GPC) to investigate the relationship between the chemical structure of lignin and its antioxidant activity. The results showed that DES treatment removed a large portion of the lignin (73.37-86.38%) from bamboo, and the chemical structure of lignin was changed due to the use of different types of HBDs. The extracted lignin exhibited good UV-vis light shielding properties, thermal stability, and antioxidant activity. Moreover, the total phenolic hydroxyl content of lignins was positively correlated with their antioxidant activity, while the molecular weight of lignins was negatively correlated with their antioxidant activity. Notably, lignin extracted with choline chloride-p-toluenesulfonic acid had the highest phenolic hydroxyl content and lower molecular weight, showing the strongest antioxidant activity (IC50DPPH = 417.69 μg/mL, IC50ABTS = 58.62 μg/mL). This study confirms the high thermal stability, excellent antioxidant activity, and UV shielding properties of lignin extracted with choline chloride-organic acid DESs, suggesting its potential application in the fields of antioxidants and material modifiers.

Highly efficient lignin depolymerization and enhanced bio-oil upgrading via in-situ hydrogenation: Impact of lignin structure

The inherent structural rigidity of lignin poses a significant challenge to its direct hydrogenation to produce aromatic compounds, requiring harsh reaction conditions. In this study, microwave-assisted hydrothermal liquefication was employed to rapidly generate raw bio-oil under mild conditions, coupled with an in-situ hydrogenation strategy to upgrade its quality. A series of lignin substrates were characterized to establish the relationship between lignin characteristics and aromatic products. Grass lignin can produce low molecular weight bio-oil in high yields (50.4–60.7 %) within 30 min at 180 °C, which is attributed to the abundance of cleavable β-O-4 linkages in its uniform structure. In contrast, softwood lignin with abundant guaiacyl (G) units possessed a robust thermal stability, resulting in a low monomer yield, but a high selectivity to G-type products (97 %). The raw bio-oil was further upgraded through in-situ hydrogenation with Pd catalysts. Low reaction temperatures (60–100 °C) favored the hydrogenation of aromatic aldehydes and ketones to their alcohol products, while high temperatures (100–220 °C) promoted the deep hydrogenation of aromatic side chains to alkyl products. Besides, an upgraded bio-oil with a higher heating value (29.8 MJ/kg) was obtained. Furthermore, the hydrogenation mechanism was investigated through the kinetics of simulated bio-oils. The activation energy follows the order: dimer β-O-4 linkage < monomer aldehyde group < ketone group < CC linkage, which is consistent with the hydrogenation kinetics observed in real lignin bio-oil. Overall, this study highlights the impact of lignin characteristics on subsequent conversion and alsoenhances our understanding of the complex depolymerization/hydrogenation mechanisms during lignin upgrading.

Exploiting Lignin Structure and Reactivity to Design Vitrimers with Controlled Ratio of Dynamic to Non-Dynamic Bonds.

Lignin is an abundant biobased feedstock, representing the first source of renewable aromatic structures. Thanks to its high functionality in aliphatic hydroxyls (Al-OH), phenolic hydroxyls (Ph-OH) and carboxylic acids (COOH), lignin is an attractive precursor to crosslinked polymer materials. Different biobased macromolecular architectures can be designed from lignins, whose end-of-life should also be considered in the context of a circular bioeconomy. To enhance recyclability of crosslinked polymer networks, the introduction of dynamic linkages to design vitrimers is a promising strategy. In this study, Kraft lignin was chemically modified with succinic anhydride, to prepare a series of modified lignins with a controlled COOH/Ph-OH ratio, exploiting the difference in reactivity between Al-OH and Ph-OH groups. Upon crosslinking with a diepoxy, mixed vitrimer networks with variable ratios between dynamic ester bonds and non-dynamic ether bonds were synthesized. The analysis of their properties evidenced the impact of the non-dynamic linkages on the materials behaviors, including their dynamicity and reprocessing ability. Although the activation energy for bond exchange is increased, non-dynamic linkages do not hinder the reprocessability of these adaptable materials, and provide them high creep resistance. The controlled introduction of non-dynamic linkages appears as a promising strategy to enhance the properties of lignin-based vitrimers.

Investigating structural disparities and catalytic depolymerization of larch lignin for high-value biomass conversion

Understanding the structural diversity of lignin is crucial for its efficient conversion into high-value aromatic compounds. However, the impact of lignin's structural characteristics from artificial forests on catalytic depolymerization is not well understood. This study investigates the structural differences in lignin from larch trees of varying ages (10, 20, and 40 years) and anatomical parts (heartwood, sapwood, canopy, bark) to understand how these variations influence catalytic depolymerization. Polyoxometalates (POMs) were selected as catalysts due to their high efficiency in facilitating the conversion of lignin into valuable chemical products. By utilizing POMs for catalytic oxidation, we explore the relationship between lignin structure and depolymerized products, providing insights into the structural features of larch lignin. Our findings reveal that the β-O-4 content of heartwood lignin is as high as 78.7 %, while that of the canopy is lower at 67.1 %. Additionally, the unique lignin structure significantly impacted the yield and selectivity of aromatic monomers, with the highest monomer yield from heartwood lignin reaching 15.64 %, compared to the lowest yield of 7.46 % from canopy lignin. These results lay a theoretical foundation for developing efficient biomass conversion technologies and offer novel strategies for sustainable biomass utilization and environmentally friendly production.